The present invention relates to an electric blower mainly used for an electric cleaner, and in particular, it aims at reducing the size of a main body of the electric cleaner to improve usability.
As electric cleaners of the prior art, there are used mainly those of the un-circulated exhaust type shown in FIG. 24 and those of the circulated exhaust type shown in FIG. 25. An outline of the electric cleaners of the prior art will be described hereinafter.
An electric cleaner 1 of the un-circulated exhaust type shown in FIG. 24 has a hose 3 connected detachably to its main body 2. Another end of the hose 3 is provided with an end pipe 5 having a control section 4. An extension pipe 6 is attached to the end pipe 5, and a head of the extension pipe 6 is connected with a suction nozzle 7. In the cleaner""s main body 2, there is a dust chamber 8 formed in communication with the hose 3. Also provided behind the dust chamber 8 are an electric blower 10 disposed in such a manner that a suction port 9 faces toward the dust chamber 8, and a power supply unit 11 housing a cord for connection to commercial power supply, a battery, or the like.
FIG. 25 shows an electric cleaner of the circulated exhaust type. Like reference numerals are used to designate components like those of the un-circulated exhaust type. The circulated exhaust type further has the following structure in addition to the structure of the un-circulated exhaust type. A main body exhaust path 13 is formed from a discharge port 12 of an electric blower 10 to a connecting area of a cleaner""s main body 2 for connection to a hose 3. Further, there are a suction passage 14 representing an airflow pass in communication with a dust chamber 8 leading to a suction port 9 of the electric blower 10, and an exhaust passage 15 for delivering exhaust flow of air expelled from the discharge port 12 at a rear side of the electric blower 10 via the main body exhaust path 13 to a front end of the hose 3, formed respectively in the hose 3, an extension pipe 6, and a suction nozzle 7. The passages are constructed so as to be independent with respect to each other, and also separated from the open air space.
The electric blower will be described now.
Most motor units for electric blowers used heretofore in the electric cleaners have been commutator motors, which are the type generally referred to as universal motors. Lately, inverter motors have been used for the purpose of achieving reduction in size and weight by increasing speed, easiness of controlling rotational speed, cutback in power consumption, suppressing temperature rises, and so on. However, an inverter motor has an increased number of power devices in its circuit, as compared to a commutator motor. For an inverter motor consisting of windings of three phases, for instance, six power devices are required. It is therefore necessary to cool the plurality of power devices efficiently.
A structure of the conventional electric blower will be described hereinafter.
As shown in FIG. 26, the electric blower 10 comprises a motor unit 16 and a fan unit 17. A rotor 22 constructed of an armature core 19, provided with an armature winding 18 and a commutator 20 mounted on a shaft 21, is installed on an impeller-side bracket 25 and a motor-side bracket 26 in a freely rotatable manner with bearings 23 and 24. The brackets 25 and 26 compose an enclosure of the motor unit 16. A stator 29 provided with a field winding 28 on a field core 27, and a holder 30 carrying a carbon brush (not shown in the figure) are secured to the bracket 26.
The fan unit 17 comprises an impeller 31 attached to the shaft 21 of the motor unit 16, an air guide 32 disposed around the impeller 31 to form an airflow path for leading a flow of the air delivered from the impeller 31 to an interior of the motor unit 16 while gradually recovering its pressure, and a casing 33 covering them. The fan unit 17 is mounted integrally to the bracket 25. The bracket 25 is also provided with a cooling air discharge port 34 in a part thereof for discharging a portion of the airflow delivered from the impeller 31, without passing through the interior of the motor unit 16.
A circuit unit 35 for controlling electric power supplied to the electric blower 10 comprises a circuit board 38 housed in a circuit board enclosure 39, and is connected with a power supply wire 36 connected to the power supply unit 11, a signal wire 37 for transmitting an operating signal from the control section 4, and so on. The circuit unit 35 is mounted on the bracket 25 of the electric blower 10 with a screw 40. A radiating fin 42 for a power device 41 or a heat-generating component such as a triac is arranged in the circuit unit 35 in an airflow path between a cooling air inflow port 43 and a cooling air outflow port 44 in the circuit board enclosure 39, where a flow of air expelled through the cooling air discharge port 34 of the fan unit 17 flows through.
When the electric cleaner 1 is operated, the electric blower 10 produces a suctioning force. Contaminated air containing dust is suctioned from an inlet port of the suction nozzle 7, and reaches to the dust chamber 8 in the cleaner""s main body 2 through the suction passage 14 in the suction nozzle 7, the extension pipe 6 and the hose 3. The air is then guided to the electric blower 10, after the dust and the like are removed. At the same time, the power device 41 is cooled by the flow of discharge air expelled through the cooling air discharge port 34.
As described, the conventional electric cleaner divides the flow of air that passes through the fan unit 17 into a flow of air to the motor unit 16 and another flow of air to cool the radiating fin 42 in order to cool the power device 41, etc. efficiently with the radiating fin 42 of small size, regardless of whether it is the circulated exhaust type, or not. Thus, the structure needs to be such that the radiating fin 42 or the circuit unit 35 is placed downstream of the cooling air discharge port 34 of the fan unit 17. It is also necessary to separate only the power device 41 portion from the circuit unit 35, to further enhance the heat dissipation. They become a structural problem within the cleaner""s main body 2, making it difficult to reduce the size of the cleaner""s main body 2.
The following description pertains to an electric blower controlled by an inverter.
An electric blower 10 comprises an inverter motor 47 consisting of a motor unit 45 and an inverter circuit unit 46, and a fan unit 48, as shown in FIG. 27. The electric blower 10 is held so that it is pressed against a retaining rib 53 on a partition 52 having a large number of through holes 51 and separating the electric blower 10 from a dust chamber 8 via a support rubber 50 placed on an outer periphery of a casing 49.
A rotor 56 provided with a permanent magnet 54 and a shaft 55 is installed on an impeller-side bracket 59 and a motor-side bracket 60 in a freely rotatable manner with bearings 57 and 58. The bracket 59 and the bracket 60 are connected to compose an enclosure of the motor unit 45. A stator 63 constructed of a core 19 provided with a stator winding 62 in a plurality of slots formed in a manner to confront the permanent magnet 54, is secured to the bracket 60. The rotor 56, the brackets 59 and 60, and the stator 63 compose the motor unit 45.
The inverter circuit unit 46 for controlling the inverter motor 47 is mounted on a circuit board 66, which is connected with a power supply wire 64 in connection to the power supply unit 11, a signal wire 65 for transmitting an operating signal and a rotating-speed control signal for the cleaner""s main body 2, and the like. It is disposed in the vicinity of the electric blower 10. A large radiating fin 68 for cooling is attached to the heat generating components such as a switching element 67 in the inverter circuit unit 46. The radiating fin 68 is sealed with sealant 69 and tightly bonded in an area near the airflow path to prevent leakage of the air.
A position detecting means for detecting a position of the rotor 56 necessary for controlling the inverter motor 47 comprises a sensor magnet 70 provided on the rotor 56 and a position detecting element 71 such as a hole element or the like for detecting a magnetic pole of the sensor magnet 70. The position detecting element 71 is mounted on a detector board 72, which is fixed to the motor-side bracket 60, and is disposed in the motor unit 45. An output signal of the position detecting element 71 is connected to the circuit board 66 with a position detecting signal wire 73.
The fan unit 48 comprises an impeller 74 attached integrally to the shaft 55, an air guide 75 disposed around a periphery of the impeller 74 to form an airflow path for leading a flow of air delivered by the impeller 74 to an upper surface of the impeller-side bracket 59 while gradually recovering its pressure, and a casing 49 covering them. The casing 49 is constructed so as to be mounted integrally with the impeller-side bracket 59 or the motor-side bracket 60.
When the electric cleaner 1 is operated, the electric blower 10 produces a suctioning force. Contaminated air containing dust is suctioned by the suction nozzle 7, and guided through the suction nozzle 7, the extension pipe 6, the hose 3, and to the electric blower 10, after the dust is removed in the dust chamber 8 in the cleaner""s main body 2. At the same time, the radiating fin 68 disposed in the airflow path near the suction port 9 or the like of the electric blower 10 is cooled by the air flowing into the electric blower 10. Consequently, the switching element 67 (i.e. the heat-generating component on the circuit board 66) is cooled.
For the conventional electric cleaner of the foregoing structure, it is necessary to ensure air-tightness for the suctioned air in the dust chamber 8 side of the electric blower 10 in order to efficiently cool the heat-generating component such as the switching element 67, etc. with the radiating fin 68, and to dispose the radiating fin 68 in a position that allows cooling with cool air before it passes through an interior of the motor unit 45. This imposes a limitation on the location where the inverter circuit unit 46 can be arranged in cleaner""s main body 2. It also requires consideration of the sealant 69, the sealing structure and so on, to ensure the air-tightness. In addition, it requires special care for easiness of assembly. The inverter motor 47, in particular, is associated with a larger number of heat-generating components such as the switching element 67 in the inverter circuit unit 46. It is therefore necessary to take such measures as enlarging an area of the radiating fin 68. However, this leads to an upsizing of the inverter circuit unit 46, and is one of the factors that prevents downsizing of the cleaner""s main body 2.
The present invention is derived in light of the above problems of the prior arts. In particular, an electric blower of the present invention comprises a motor unit provided with a freely rotatable rotor and a stator, an impeller mounted on an output shaft of the rotor, and a fan unit comprised of a casing covering the impeller. It is provided with a circuit unit, which controls electric power to the motor unit, disposed in an airflow path for the air expelled from an outer periphery of the impeller and delivered to the rotor and the stator of the motor.
Further, an electric cleaner of the present invention comprises a dust chamber for collecting dust, a suction port connected in communication to the dust chamber, and the above-said electric blower.